One of the reasons why we should know how nuclear weapons work is that the world has entered explosively into a nuclear age on July 16, 1945. On that day, the United States planned to test a weapon that was not known before. That took place in the New Mexico desert. Made of a ball of plutonium the size of a tennis ball, the Trinity bomb exploded as equivalent to 20,000 tons of TNT.
The construction principles and the ability to destroy nuclear bombs have remained unchanged for 50 years. The materials that emit radiation (uranium, plutonium, tritium, etc.) and the various radioactive rays in the universe (alpha, beta, gamma, cosmic X rays / solar or radon) are common to the terrestrial ecosystem. In the late nineteenth and early twentieth century, many physicists have conducted experiments aimed at identifying all the properties of electricity. Incidentally, they discovered radioactivity.
In those years, most scientists imagined that future applications of new discoveries would be extremely beneficial for humanity. W. Roentgen, for example, has realized that they will revolutionize medicine from the first moments after producing X-rays.
However, during World War II, Germany took advantage of physical geniuses such as Werner Karl Heisenberg and Otto Hahn and made them develop the first nuclear program in the world. Luckily, the Nazi nuclear program failed, but once the nuclear threat was launched, most of the powers entered the arms race. The star of nuclear technology was called an atomic bomb.
The Manhattan Project
In 1939, the intelligence of the United States already knew that the Nazis were planning the construction of the atomic bomb.
Consequently, three years later, the United States began its own nuclear program, entitled Manhattan Project within the Army Corps of Engineers (Department of US Army Scientists), under the command of General Leslie R. Groves. General Groves’s secret mission was to establish three centers for nuclear engineering and production, for which he named the physicist J. Robert Oppenheimer, who also laid the foundations: Clinton Engineer Works at Oak Ridge, Hanford Engineer Works in Eastern Washington State and Project Y in Los Alamos, State of New Mexico.
Meanwhile, in a small secret laboratory in the basement of the University of Chicago, General Groves appointed Italian physicist Enrico Fermi, Nobel Prize winner and refugee, to create a controlled nuclear reactor. On December 2, 1942, Fermi completed the construction of Chicago Pile One (CP-1), the world’s first controlled nuclear reactor.
For the first time in history, man had tremendous energy released by a nucleus. Immediately, the CP-1 was taken in Oak Ridge and Hanford so that Oppenheimer and other scientists could find a way to obtain nuclear fuel and, once the operation is completed, use the reactor to build an atomic weapon.
In 1942, the only solutions for this fuel were uranium (U-235) and plutonium (Pl-239). Manhattan Project managers had no idea how fast and how much nuclear fuel the two substances would produce, so they decided to simultaneously build atomic weapons on both elements. Although the main scientists working on the project were in Oak Ridge and Washington (these bases benefit from the latest technology), the first atomic bombs were built in Los Alamos.
Based on a very simple element, the gun barrel, those inside the Project Y performed a U-235 bomb: one capsule with U-235 was sent, through a tube, to another U-235 capsule. When the two amounts of uranium were combined, the nuclear explosion occurred.
A second bomb used implosion to detonate the plutonium. More explosions surrounded the ball of plutonium, it was compressed and this phenomenon caused a nuclear explosion.
The two bombs were named Little Boy and Fat Man.
The manufacture of nuclear bombs involves the development of a technology that stabilizes the nucleus of extremely unstable atoms and makes them emit the nuclear energy they contain on demand. This technology is achieved through two methods: nuclear fusion and fission. Both processes result in the release of huge amounts of heat and radiation.
To build an atomic bomb, you need a fuel source to activate fission or fusion, a firing device and a technology that allows the fuel to generate nuclear fission or fusion before the explosion occurs.
In a fission bomb, fuel must be stored in separate subcritical masses that can not be fissioned, to avoid premature detonation. The critical mass needed to produce a nuclear reaction is the smallest part of the material used to build the bomb. After facing a series of problems, the managers of the Manhattan Project have resorted to two solutions: a firing mechanism similar to that of a gun barrel and an implosion technique.
The latter is achieved through a neutron generator, which consists of a small helix and several sheets of polonium and beryllium that separated the nuclear fuel. The way the generator works is extremely simple: the helix combines the two sub critical masses and the polonium spontaneously emits alpha particles. Ultimately, they produce beryllium-8 that releases neutrons. Then neutrons initiate fission.
This model, also called a thermonuclear pump or H (helium) pump, would, in theory, be more efficient than fission pumps. Stanislaw Ulam, from Poland, joined the Manhattan Project and was able to produce a hybrid thermonuclear bomb in 1945 at Los Alamos.
The Ulam pump is actually an implosion type fission bomb that contains a mini fusion bomb.
- The fission pump causes implosion and emits X-rays, producing high temperatures and pressures.
- The compression shock initiates the fission reaction in the plutonium and exudes radiation, more heat and neutrons.
- Neutrons interact with lithium, transforming it into tritium.
- The combination of enormous temperatures and pressures causes a fusion reaction between tritium and deuterium, which amplifies radiation and heat, producing neutrons.
- They induce fission in uranium-235 pieces.
- The bomb explodes.
On August 6, 1945, the weather was beautiful in Hiroshima, the first target city chosen by the Americans. At 8.15 am local time, the Enola Gay bomber launched Little Boy. The bomb exploded at 580 meters above the city.
Two thirds of the city were destroyed. Within a radius of 10 kilometers, nearly 90,000 buildings have collapsed instantly.
11.02 a.m., August 9, 1945: Fat Man was detonated 500 meters above Nagasaki.
Fat Man was destined for the city of Koruka, but he was saved due to the dense fog he had left in the morning’s attack. About 40% of Nagasaki was destroyed. Although the Fat Man bomb was more powerful than Little Boy, the rugged terrain of the city saved many inhabitants. 25,000 of the 270,000 died on the day of the explosion. But 50,000 more died at the end of the year due to radiation.
If the objective of detonation of a nuclear bomb is a populated area, the explosion produces devastating losses. Damages vary according to the distance between the ground and the center of the explosion, called the hypo or zero point center. The smaller the distance, the greater the effect.
The destruction and the victims are caused by four factors:
- the intense heat wave That arises because of the explosion;
- the Pressure caused by the shock waves produced by the explosion;
- the radiations emitted by the pump;
- the rain effect: radioactive clouds that remain after the explosion and radioactive particles formed from the remains of the bomb, which eventually fall to the ground.
At the zero point, everything evaporates instantaneously due to extremely high temperatures (more than 300 million degrees Celsius). In a radius of 10 to 15 kilometers, the heat of the explosion causes fatal burns or instant combustion and the pressure of the explosion causes all the buildings to collapse. In areas near the explosion, victims die from heat, acute exposure to high radiation and devastating fire.
In the long term, the effect of the disaster causes the consequences to spread in a vast space: the radioactive particles are transported by the wind and / or penetrate into the water sources. People who are thousands of kilometers away from the explosion are exposed to lethal radiation.
Researchers from the Radiation Effects Research Foundation (RERF) have studied survivors of the Hiroshima and Nagasaki bombings to understand the effects of the nuclear explosion on human health.
They were the first to show that radiation and the effect of precipitation mainly affect all cells that are actively dividing (hair, intestines, reproductive organs). In a first phase, exposure to radiation leads to dizziness, vomiting, diarrhea, massive loss of hair and teeth, cataracts and loss of a large number of cells.
In a second phase, the victims show an increased risk of getting cancer or leukemia, becoming infertile or giving birth to children with birth defects.
In the 1980s, several physicists hypothesized that, due to the Cold War and the global armed forces without a protocol to control the proliferation of nuclear weapons, there is a theoretical possibility that more bombs of this type could explode simultaneously in different parts. of the world. This disaster would cause the nuclear winter.
The scenario that underlies this hypothesis is that the explosion of more than 50 nuclear bombs would rise in the air huge clouds of toxic radioactive dust that would penetrate the Earth’s atmosphere. Finally, the radioactive layer would block the sunlight that would lead to the end of the photosynthesis process. The last consequences of nuclear winter would be the disappearance of all sources of food, of all vegetation and of all animals on Earth, which would implicitly lead to the disappearance of the human race.
The nuclear winter scenario has acquired the valences of a terrifying collective fear when Saint Helen volcano, United States and Pinatubo in the Philippines exploded. The giant clouds and dust crossed thousands of kilometers, darkening the sky and destroying the flora and fauna of many areas. The two disasters have shown that, in the case of an atomic war, the nuclear winter scenario is likely to become a reality.
Limiting the spread of nuclear danger
While nine nations have nuclear weapons, another 187 pledged not to produce them. Twenty countries such as Switzerland, Brazil, Argentina, Canada and South Africa had programs once, but as signatories of the 1968 Nuclear Non-Proliferation Treaty they abandoned them.
The treaty was designed to limit the spread of nuclear weapons and to compel the five states that had to share nuclear technology and materials for their use in peaceful areas. The treaty obtained the dismantling of 38,000 warheads since 1986 mainly due to the disarmament of the United States and Russia.
The 1996 Comprehensive Nuclear-Test-Ban Treaty (CTBT) is an attempt to limit detonations and curb nuclear weapons, but the United States Senate refused to ratify it in 1999.
Another big challenge is to control the amount of Russia’s vast and poorly protected nuclear arsenal. The G8 countries have repeatedly pledged billions of dollars to protect the huge deposits.
The International Atomic Energy Agency is fighting to control the theft and black market of nuclear materials and technologies, and fears that terrorists may obtain a counterfeit bomb are often expressed. The sale of materials and information was highlighted in 2004 when a nuclear scientist admitted that Pakistan sold nuclear technology to Libya, North Korea and Pakistan.
The generation of nuclear energy has been linked to nuclear proliferation. In fact, the first industrial-scale reactors built in the United States in 1944 were designed to produce plutonium for weapons and the energy created was wasted. The first nuclear reactor that provided electricity to the national grid was inaugurated in 1956 in England, at Calder Hall. Today, countries such as Japan and France use nuclear energy to provide up to 75% of their energy.
Unlike nuclear weapons, nuclear reactors must closely control the chain reaction of fission. To avoid an out-of-control reaction, the control rods are intertwined with uranium or plutonium fuel rods. The control rods absorb the neutrons and can be lowered to the reactor core to regulate the energy produced. A moderating substance, such as water or graphite, surrounds the bars that reduce the neutron reaction by reflecting them back in the center.
A cooling agent circulates around the core and is pumped to a heat exchanger where the water turns into steam and operates turbines that generate electricity. Modern gas-cooled reactors, such as in the United Kingdom, use compressed carbon dioxide as a refrigerant. Light, pressurized and heavy water reactors use water as a moderator and coolant.
These reactors are inherently inefficient, since they use only about 1% of the energy stored in the uranium fuel. To overcome this inefficiency and minimize nuclear waste, some countries reprocess nuclear fuel. The reprocessing unit in Sellafield, United Kingdom, is the largest in the world, but it had many problems.
Modern (but less safe) breeding reactors use liquid sodium metal as a coolant and generate plutonium as a fuel. Reproductive reactors such as Superphenix in France, Dounreay in the United Kingdom, Monju in Japan and planned reactors in India can use up to 75% of the energy contained in uranium. The new Rapid-L miniature reactors could reach the power supply in the basement of apartment buildings and portable reactors (# 8220; take-away and # 8221;) are planned in the future.
Nuclear fuel was also used to power submarines, such as the damned Kursk of Russia; spacecraft such as Cassini, Galileo and the one that failed, Mars-96; Icebreakers, aircraft carriers and other vessels. The Pentagon briefly evoked the idea of a nuclear-powered aircraft.
Some accidents destroyed public confidence in nuclear energy. The worst nuclear accident in the United States occurred in 1979, when the refrigeration system malfunctioned at Three Mile Island in Pennsylvania. The reactor has melted, releasing radioactive gases into the environment. Now there are concerns about the safety of the old reactors in the United States.
The most catastrophic nuclear accident in the world occurred in Chernobyl, Ukraine. The control rods were removed from the reactor during a poorly conducted test, which melted and caused massive explosions. The radiation released directly killed 30 people and spread throughout northern Europe.
The radiation caused by the accident caused thyroid cancer and leukemia, birth defects, infant death and contamination of lakes and forests. Three other reactors at Chernobyl were restarted in 1988, but then halted, the last in 2000 after Western nations paid Ukraine for closure. Similar reactors in Eastern Europe can be equally dangerous.
In 1999, 70 people were exposed to radiation at the uranium processing factory in Tokaimura, Japan, after workers added seven times more uranium than the safe amount in a stabilizer tank. This triggered an uncontrolled chain reaction. Many other dangerous or fatal accidents occurred in Windscale, Sellafield, Mayak, Monju, Tsuruga and Mihama.
On March 11, 2011, there was a disaster explosion at the Fukushima nuclear power plant in Japan, which consists of four nuclear reactors. It was caused by the earthquake in the northeast region of 2:46 PM, followed by a large tsunami.
Radioactive nuclear waste, which remains dangerous for thousands of years, is another serious obstacle for the industry. As ways to get rid of it, governments have considered:
- burial deep underground, as in the Yucca mountain in Nevada, USA. UU;
- transportation in other countries;
- damage by laser;
- Its incrustation in glass blocks in nuclear facilities.
The areas that use nuclear power plants include North America, Japan and Europe.
The advantage of nuclear energy is that it does not release carbon dioxide and other gases harmful to the atmosphere.
The disadvantage is that nuclear reactions produce radioactive wastes that can be extremely dangerous. People who work near radioactive waste must take strict measures to guarantee their health, safety and protect the environment.
Nuclear power plants are expensive, both for construction and for maintenance. This is the reason why there are fewer power plants in the world lately.